The invention relates in particular to the scanning technique based on ultra-sound according to the impulse-echo principle. This technique is generally performed in one of two possible manners.
The first is the use of the socalled B-scanning, which normally implies the scanning of a sectional plane through the object and a running registration of the positions of reflecting structures in the said sectional plane. The result is that after a few minutes of scanning it will be possible to have drawn up a two-dimensional picture on a storage-oscilloscope, showing the intersections of the reflecting structures with the sectional plane.
The second is the use of socalled dynamic scanning, which implies a rapid scanning of a limited area permitting utilization of the short-time memorizing of the eye for the formation of a picture.
B-scanning by way of a storage-oscilloscope represents the most widely used procedure, but it has a major drawback in that it takes a long time to draw up a satisfactory picture. It is accordingly required to form the entire picture before it is possible to see whether it is satisfactory, and then to wipe it off again entirely to adjust amplification etc.m before the next picture is registered. In the meantime, however, the conditions to be examined may have changed.
This may, for instance, be the case, if we are dealing with a fetus, which is moving. If we examine parts of the human body we have moreover no clear impression of the relation of the sectional picture to the body, as picture and body are placed at some distance from each other.
Dynamic scanning represents a more recent method, which in certain relations offers improvement in comparison with the B-scanning. Due to the rapid, automatically repeated scanning it is easier to make adjustments to obtain a better picture, as it will be possible to detect alterations instantly. Nor will there be any problems with regard to alterations of the conditions of the examined object, as it will be possible to ascertain such alterations directly during the scanning.
In spite of these improvements of the manner of producing the scanning pictures, there will still remain two problems unsolved:
1. You will only get a picture answering the section of the body being examined, which will complicate the formation of a picture of the entire spatial form and extent of a given structure. PA1 2. You will have no direct idea of the position of the the examined body reproduced. Alterations of the scanning angle and position will bring about a change of the picture, but due to the appearance of the picture on a stationary screen, no particularly good impression of the position of a depicted structures is left.